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| United States Patent |
5,192,137
|
|
Renard
|
March 9, 1993
|
Flexible plain bearing and its application to motor vehicle steering
mechanisms
Abstract
This bearing comprises an outer ring (11) made from a sleeve (110) which is
delimited by an outside wall (111) and an inside wall (112) and which
carries on its outside wall (111) a bush (1111), an inner ring (12) which
is made from a sleeve (120) which is delimited by an outside wall (121)
and an inside wall (122) and which carries on its inside wall (122) a bush
(1221), a link (13) located out of plumb with the bushes (1111, 1221) in
order to connect these rings (11, 12) while allowing only a relative
rotation between them (11, 12).
Application to motor vehicle steering columns.
| Inventors:
|
Renard; Henri J. A. (Seloncourt, FR)
|
| Assignee:
|
ECIA (FR)
|
| Appl. No.:
|
795388 |
| Filed:
|
November 21, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
384/275; 384/192; 384/296 |
| Intern'l Class: |
F16C 017/10; F16C 023/04 |
| Field of Search: |
384/192,215,223,220,275,295-297,202,203
|
References Cited
U.S. Patent Documents
| 3604765 | Sep., 1971 | Babcock | 384/192.
|
| 4415166 | Nov., 1983 | Beia | 277/51.
|
| 4603982 | Aug., 1986 | Dittrich | 384/129.
|
| 4756249 | Jul., 1988 | Hardin | 384/215.
|
| 4854745 | Aug., 1989 | Kamimura et al. | 384/420.
|
| Foreign Patent Documents |
| 1297406 | May., 1962 | FR | 384/220.
|
| 2537674 | Jun., 1984 | FR.
| |
| 2004956 | Apr., 1979 | GB.
| |
Primary Examiner: Hannon; Thomas R.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
Claims
I claim:
1. Flexible plain bearing for mounting a shaft on a support coaxially in
such a way that only one degree of freedom in relative rotation between
shaft and support is possible, this bearing (10) being characterised in
that it comprises an outer ring (11) made from a sleeve (110) which is
delimited by an outside wall (111) and an inside wall (112) and which
carries on its outside wall (111) in the proximity of at least one of its
ends a protruding bush (1111), engaged in this outer ring (11) an inner
ring (12) which is made from a sleeve (120) which is delimited by an
outside wall (121) and an inside wall (122) and which carries on its
inside wall (122) in the proximity of at least one of its ends a
protruding bush (1221), a link (13) located out of plumb with the bushes
(1111, 1221) in order to connect these rings (11, 12) while allowing only
a relative rotation between them (11, 12), made by a female element (131)
carried by one of these facing walls (112, 121) of the rings (11, 12) and
made by a male element (132) carried by the other of these facing walls
(112, 121) of the rings (11, 12), these male and female elements (132,
121) being coupled to each other by mutual engagement.
2. Bearing according to claim 1, characterised in that the cross-section of
these male and female elements (132, 131) is angular, particularly in
Greek key-pattern.
3. Bearing according to claim 1, characterised in that the cross-section of
these male and female elements (132, 131) is curved, preferably as an arc
of a circle.
4. Bearing according to claim 1, characterised in that the cross-section of
these male and female elements (132, 131) is spherical.
5. Bearing according to any one of claims 1 to 4, characterised in that at
least one of the sleeves (110, 120) is provided with slots (113, 123)
which between them delimit tongues (114, 124) and in that this link (13)
is at least partly carried by these tongues (114, 124).
6. Bearing according to claim 1, characterised in that the male element
(132) is carried by the inside wall (112) of the outer ring (11) and the
female element (131) is carried by the inside wall (122) of the inner ring
(12).
7. Bearing according claim 1, characterised in that the male element (132)
is carried by the outside wall (121) of the inner ring (12) and the female
element (131) is carried by the inside wall (112) of the outer ring (11).
8. Bearing according to claim 1, characterised in that the rings (11, 12)
are each made from a synthetic material and in that the pair of these
synthetic materials in particular provides flexibility, a small
coefficient of friction and lack of tendency to creep, endurance and
resistance to wear.
9. Bearing according to claim 8, characterised in that the materials are
chosen in particular from polyacetals, polypropylenes, polyamides and
polyethylene glycol terephthalates.
10. Bearing according to claim 9, characterised in that the materials are
loaded with at least one lubricating substance chosen from graphite,
molybdenum disulphide, polytetrafluoroethylene and silicones in
particular.
11. Application of a bearing according to claim 1 to a land motor vehicle
steering column.
Description
The present invention relates to flexible plain bearings intended to
provide the link between a shaft and a support in such a way that only one
degree of freedom in relative rotation between shaft and support is
possible; the invention also relates to the application of such a bearing
to motor vehicle steering columns in particular.
In many industrial sectors it is necessary to be able to mount a shaft on
at least one support in such a way that this shaft and support can only
turn in relative rotation about their common axis without in so doing
being able to displace themselves in translation along this axis.
Such a situation is encountered for example in the motor vehicle industry
in the assembly of steering columns.
As known, conventionally, a steering column is formed from a support,
column holder or tube which is fixed to the driving post of the vehicle by
the intermediary of fixings, lugs or similar items. Such a steering column
is also formed from an actual shaft which, by the intermediary of the
steering wheel, transmits the instructions from the driver to the steering
wheels of the vehicle by the intermediary of a steering box and steering
gear. This shaft is mounted, at least partially, in this support, holder
or tube by means of bearings, most often roller bearings, in order to
allow only one degree of freedom of relative rotation about the common
axis of the shaft and of this support, holder or tube, to the exclusion of
any other degree of freedom such as an axial translation.
Such a subassembly which takes an active part in the safety must be
reliable, must satisfy strict and sometimes apparently contradictory
standards while remaining of moderate cost.
Such a steering column must for example:
be free of any play without the slightest gripping preventing the
displacements,
allow a rotation with a torque which does not exceed 0.2 Nm,
have a long-time resistance to wear which conventionally corresponds at
least to the average estimated service life of the vehicle,
withstand the radial compression stresses which can occur during a theft
attempt while the anti-theft lock is engaged, under the effect of a torque
of 250 Nm,
withstand, by means of its stiffness, a bending moment resulting from a
radially applied force on the steering wheel in the order of 1 kN/mm,
resist any longitudinal translation of the shaft with respect to the
support, by sliding.
This brief and non-exhaustive list shows how difficult it is to comply with
all of these technical requirements taking account of the financial
imperatives which must be considered.
A solution normally used for overcoming this type of difficulty consists in
using very special ball or roller bearings, which are very different from
the bearings with circular, conical or spherical tracks. In fact, the
bearings used for this type of application have, for example, polygonal
and often triangular tracks. These bearings allow for the variations in
dimensions resulting from manufacturing tolerances between support, tube
or holder and shaft to be compensated, while ensuring the total absence of
play, as recalled above.
The purpose of the invention is to produce a flexible plain bearing for
mounting a shaft on a support in such a way that only one degree of
freedom in relative rotation between shaft and support is possible and
which, even though having a moderate manufacturing and assembly cost,
allows most of the technical requirements which have been mentioned
previously to be satisfied.
The subject of the invention is a flexible plain bearing for mounting a
shaft on a support in such a way that only one degree of freedom in
relative rotation between shaft and support is possible, and which is
essentially constituted by an outer ring and an inner ring engaged in the
latter. This bearing is notable in that the outer ring is made from a
sleeve which is delimited by an outside wall and by an inside wall and
which carries on its outside wall in the proximity of at least one of its
ends a protruding bush, in that engaged in this outer ring is an inner
ring which is made from a sleeve which is delimited by an outside wall and
by an inside wall and which carries on its inside wall in the proximity of
at least one of its ends a protruding bush, and in that a link is located
out of plumb with the bushes in order to connect these rings while
allowing only a relative rotation between them, this link being made by a
female element carried by one of these facing walls of the rings and a
male element carried by the other of these facing walls of the rings,
these male and female elements being coupled to each other by mutual
engagement.
The subject of the invention is also the application of such a bearing to a
motor vehicle steering column.
Other features of the invention will emerge on reading the following
description and claims together with an examination of the appended
drawing, given solely by way of example, in which:
FIG. 1 is a diagrammatic central cross-section of an embodiment of a
flexible plain bearing according to the invention in its application to a
steering column;
FIG. 2 is an exploded perspective view of this embodiment of a flexible
plain bearing according to the invention; and
the other FIGS. 3 to 11 are views in elevation with partial cross-section
of other variant embodiments of a flexible plain bearing according to the
invention.
As flexible plain bearings and motor vehicle steering columns are well
known in the art, only that which directly or indirectly concerns the
invention will be described below. For further information, those skilled
in the art in question will refer to the conventional current solutions
available to them in order to deal with special problems with which they
are facing.
In the following description the same reference number is always used to
identify a like component, whatever the embodiment or its variant may be.
For convenience of explanation, each of the components of the invention
will first be described before explaining its assembly and operation
The features of a flexible plain bearing according to the invention will be
described in its particular application to a motor vehicle steering column
but it is clear that the plain bearing according to the invention has
other applications.
As can be seen in FIG. 1, a motor vehicle steering column D is essentially
composed of a support S and a shaft A which are coaxial. The support S
which is in the form of a holder or tube is fixed to a structure or shell,
which is not shown, of a driving post by means of fixings F or similar
items. A steering wheel V, fixed to one of the ends of the shaft A, is
intended to rotate it about the common axis X--X, without this shaft being
able to slide in translation along this axis in so doing.
In order to achieve this, there is interposed between shaft and support at
least one flexible plain bearing according to the invention. As can be
seen, this bearing 10 comprises an outer ring 11 in which is engaged, at
least partially, an inner ring 12.
As can be seen, the outer ring 11 is made from a sleeve 110 which is
delimited by an outside wall 111 and an inside wall 112. In the proximity
of at least one of the ends of this sleeve 110, the outside wall 111
carries a protruding bush 1111.
The inner ring 12 is made from a sleeve 120 which is delimited by an
outside wall 121 and an inside wall 22. The sleeve 120 carries, in the
proximity of at least one of its ends and on its inside wall 122, a
protruding bush 1221.
A link 13, located out of plumb with the bushes 1111 and 1221, allows the
rings 11 and 12 to be connected in such a way as to prevent any relative
translation along the X--X axis but while allowing only a relative
rotation between them. This link 13 is made by a female element 131
carried by one of the facing walls 112, 121 of each of the rings 11 and
12, and is also made by a male element 132 carried by the other of these
facing walls 112, 121 of the rings 11 and 12. These male and female
elements 132 and 131 are coupled to each other by preferably elastic
mutual engagement as will be understood below.
As can be observed in the various figures of the drawing, the central
cross-section of the male and female elements 132 and 131 of the link 13
is angular, approximately in Greek key-pattern (FIGS. 3, 4, 5, 9, 11) or
curved, preferably as an arc of a circle (FIGS. 6, 8, 10), or spherical
(FIG. 7).
If necessary at least one of the sleeves 110, 120 is provided with slots
113, 123 respectively. These slots, which for example emerge at one of the
ends of a sleeve, between them delimit tongues 114, 124 respectively. As
can be seen, the link 13 and in particular its female 131 and/or male 132
elements are carried at least partly by these tongues 114, 124.
As can be seen, according to the embodiments and the variants embodiments,
the male element 132 is carried by the inside wall 112 of the outer ring
11 while the female element 131 is carried by the inside wall 122 of the
inner ring 12. It is clear that the opposite solution could be used, that
is to say that the male element 132 is carried by the outside wall 121 of
the inner ring 12 and the female element 131 is then carried by the inside
wall 112 of the outer ring 11, as shown in FIG. 7.
The outer 11 and inner 12 rings of the bearing 10 according to the
invention are assembled and mounted as shown in particular in FIG. 1; as
can be understood the bush 1221 protruding from the inside wall 122 of the
sleeve 120 of the inner ring 12 provides the grip on the shaft 1.
Similarly, the bush 1111 protruding from the outside wall 111 of the
sleeve 110 of the outer ring 11 provides the grip on the support S, as
shown in FIG. 1.
Because of the position adopted for the male and female elements 132 and
131 respectively of the link 13 out of plumb with the bushes 1111 and
1221, it is observed that the guidance in rotation is absolutely
independent of the forces and reactions which develop at the level of the
bushes.
Owing to this solution, a flexible plain bearing is obtained which has a
high degree of guidance in rotation, which practically prohibits any
longitudinal sliding because of the large forces developed at the level of
the bushes, and great radial stiffness.
The choice of the elasticity of the materials from which the rings are
made, and the possible presence of slots which delimit tongues in them,
allow a greater flexibility to be obtained which favours assembly and/or
functioning.
Preferably, at least one of the rings 11 and 12 is made from a synthetic
material and when two synthetic materials are used the pair of these
materials chosen is that which offers the desired flexibility, coefficient
of friction and lack of tendency to creep, endurance, resistance to wear
etc.
Among the materials which can be used, polyacetals, polypropylenes,
polyamides and polyethylene glycol terephthalates will be mentioned in
particular.
If necessary, these materials are "loaded" with at least one lubricating
substance chosen for example from graphite, molybdenum disulphide,
polytetrafluoroethylene and silicones in particular.
The rings of a bearing according to the invention are manufactured for
example by injection moulding.
As can be understood, the assembly of the two rings of a bearing according
to the invention is preferably carried out previously by mutual elastic
fitting before they are used; if necessary each of these rings can first
be positioned on the shaft and the support respectively and these rings
are then connected.
It will be observed that what is essential is the absence of play and the
very strong longitudinal holding of each of the rings on the shaft and in
the support respectively.
All the attraction and the advantages provided by a flexible plain bearing
according to the invention can be understood immediately from the above
description.
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